Re: 300 SAUM load advice.
I have had horrible luck with the 190 SMKs, because of the seating depth issue (that's what I blamed it on). Varget has been the best powder in both of mine for bullets 175 grs and lighter. I shoot the 185 gr Berger VLDs instead of the SMKs for their better bc and because I can load them in my factory chamber into the lands with the top of the BT at the shoulder/neck junction. They just work perfectly. I went up to 64 gr H4350, but pressures got a bit iffy. The load I settled in on is 60 gr of H4350 with the 185 gr Berger VLDs. That gets me 2900 fps with them. I shoot the 175 gr SMKs with 53.5 gr Varget or the 178 gr AMAX with 54 grs Varget which net 2880-2920 for the SMKs and 2820-2860 for the AMAX, depending on the ambient temps. From my hunting nook across a creek bottom to another ridgeline about 400 yards away, the SMKs print about 4" higher.
I played with primers to tighten up the groups with the 185s. I tried BR2s, WLR, RP9.5M, GM210M and WLRM primers. Personally, I have always had the best groups and usually velocity with the RP9.5M primers.
Its my opinion, but I think they are the idea primers for about 60 gr of powder. On the average of all my rifles, BR2s work the best under powder charges of about 38-45 grs, WLR are in the 50-60 range, RP9.5Ms seem to take over up to around 75 grs where WLRM and 215s take over. To throw some mud into this, my 300WM shoots 81gr H1000 and 175 gr SMKs into 0.5" groups at 200m with the BR2s. When I tried the RP9.5Ms, groups opened to 1". 'Hotter' primers made things worse and put me into pressure signs.
On the 200 SMKs, I think H4350 will still be your best bet. You should be able to hold 2800 fps with them or better since you have a min-spec chamber. FWIW, my factory chamber is pretty dang close to min-spec best I can measure. Best of luck! I am interested to see what you are able to work up.